Deck building games are one of our favorites. Dominion was the first of its kind to have the deck building happen during the game instead of building your deck before the hand like with trading card games. Dominion (especially with all its expansions) has tons of different cards you can play with but each time you play there are only 16 options of cards you can buy. Six of those stacks are always the same and the other ten can be selected by the players, chosen from suggested setups, or using the randomizer cards to pick randomly to get great variety in game play.
Each player starts with the same 10 card hand. The goal of the game is to buy cards that help you make your deck a better point making engine than the rest of the players. With different cards available each game, it can be an interesting puzzle to decide which cards and how many of each to try to buy and shuffle into your deck. Part of the limiting factor of the game is unless you have cards that give you more you can only play one action card per turn and can only buy one card as well.
Since there are so many different card combinations sometimes there can be disagreements over how those cards interact, but over time the designers have gotten clearer in their wordings and also the rules books have a section talking about possible interactions between the available cards to clear up any rules argument that might pop up.
Newer games have given the deck building style a little more polish in our opinion. However, the designers have also worked to add polish to Dominion itself - with a great many expansions and more likely to come. If you want to see where this great style of game started make sure to give Dominion a look!